In many countries prostate cancer is the most common, or the second most common, cancer diagnosed in males. Similarly, breast cancer is the most common, or the second most common, cancer diagnosed in females in many countries. There are many common epidemiological, genetic, biochemical and mechanistic aspects of these two cancers. Incidence rates, lifetime risks, dietary factors (especially diets high in fat and low in fiber), death rates, ethnic trends and country of residence are among the common epidemiological features. In addition, steroid hormones play an important role in the pathogenesis of both cancers. Unless detected early, prostate and breast cancer may spread to the spine and bones of the patient, causing severe pain, bone frailty and death.
The same general range of treatment options exist for both prostate and breast cancers, namely surgery, radiation and hormone ablation/depletion. Hormone-ablation or depletion treatment (for example, blocking androgen production or activity) is frequently prescribed for metastatic cancers, however the cancer may become resistant to hormone ablation therapy and chemotherapy often becomes a final option for treatment. Life quality often deteriorates during chemotherapy and life expectancy is generally limited. One of the major side effects of chemotherapy is the destruction of the body's immune system.
Androgens, such as testosterone, are the key drivers of prostate cancer. The most convincing demonstration of androgen involvement is the dramatic reduction of prostate cancer risk in prepubertal castrates. The active metabolite of testosterone, dihydro-testosterone, is generated by the action of the enzyme 5α-reductase. In females, estrogen stimulates the growth of many breast cancers. Such cancers have estrogen receptors on the surface of their cells and are called estrogen receptor-positive (ER-positive) cancer. Breast cancer patients with ER-positive tumors generally have a more favorable prognosis than those with ER-negative tumors, and such patients can generally be successfully treated with hormonal therapies such as tamoxifen and aromatase inhibitors. In contrast, women with HER2 (human epidermal growth factor receptor)-positive breast cancer have a more aggressive disease and a higher risk that the disease will recur than women who do not have HER2-positive cancer.
Androgens and estrogens are steroid hormones which exert their actions by binding and activating transcription factors which form the steroid hormone receptor family. These transcription factors, in turn, regulate a large number of other genes. Steroid hormones with very different biological activities can be inter-converted by the action of enzymes. Tissues that were traditionally thought to be responsive to one class of such steroids are now known to contain receptors for other classes. For example, the breast has androgen receptors in addition to estrogen and progesterone receptors, and the prostate has estrogen and progesterone receptors in addition to testosterone receptors.
Blockade of hormone action (such as androgen or estrogen action) by pharmacological agents often confers primary protection against the cancer. Such pharmacological agents may directly kill the target prostate cancer or breast cancer cells, or may slow their growth rate or impair their metabolic activity. This can result in a partial and incomplete apoptotic state.
Pharmacological agents used in the treatment of cancers, such as prostate and breast cancers, include immune activators, such as interleukin 2 (IL2) which is a specific T cell growth factor, granulocyte-macrophage colony stimulating factor (GM-CSF; also known as sargramostim; trade name Leukine®), and granulocyte colony stimulating factor (G-CSF; also known as filgrastim; trade name Neupogen®). IL2 was initially used mainly as an in vitro stimulant in cancer therapy to augment specific CD8-positive T cell mediated anti-tumor immunity and activation of non-specific cytolytic effector cells, termed lymphokine-activated killer (LAK) cells. IL2 can induce the proliferation and expansion in number of tumor-reactive T cells in vitro, and T cells grown in culture with IL2 can be effective reagents in vivo for specific tumor therapy. T cells cultured long-term in vitro with IL2 are functionally limited in vivo without the administration of exogenous IL2. In contrast, T cells grown in vitro with specific antigen, as opposed to IL2, as the major stimulus for proliferation are able to proliferate rapidly in vivo, and distribute widely in host lymphoid organs. IL2 has negative side effects in vivo which limit its clinical use.
Both GM-CSF and G-CSF were initially developed for the rapid restoration of neurophils following whole body irradiation and for use in other disorders characterized by neutrophil deficiency. Administration of GM-CSF has been demonstrated to lead to long-term control of prostate cancer in a substantial number of patients (Rini et al., J. Urol. 2006, 175(6):2087-91).
The autologous cellular immunotherapy Provenge® (sipuleucel-T; Dendreon Corp., Seattle, Wash.) was recently approved in the US for treatment of asymptomatic or minimally symptomatic metastatic castrate resistant (hormone refractory) prostate cancer. In this therapy, white blood cells (primarily antigen presenting, or dendritic, cells) are isolated from the patient and incubated with a fusion protein comprising a fragment of prostatic acid phosphatase (PAP; known to be present in 95% of prostate cancers) chemically bound to GM-CSF. The resulting activated cells are then administered back to the patient. The activated dendritic cells have, as their primary function, the activation of cytotoxic CD8+ cells in the patient which then target and kill prostate cancer cells expressing PAP antigens. Only a patient's own dendritic cells can be used, due to the requirement for histocompatibility between the dendritic cells and specific CD8+ cytotoxic T cells. The recommended course of therapy for Provenge® is three complete doses, given at approximately 2-week intervals. The biggest drawback to this therapy is its high cost.
Filgrastim (G-CSF) is approved for use in cancer patients with bone marrow damage due to chemotherapy or radiotherapy. It has been shown that patients treated with filgrastim have fewer infections, less need for intravenous antibiotics, and shortened hospital stays compared to those who do not receive the drug. Filgrastim is often used in breast cancer treatments. Both GM-CSF and G-CSF have similar biological profiles, with G-CSF being the more potent stimulator of neutrophil regeneration.
Another therapeutic agent employed in the treatment of prostate cancer is ketoconazole, a synthetic drug that was originally developed as an antifungal agent. In a clinical trial, ketoconazole was shown to have a 50% response rate in hormone refractory prostate cancer. Significant side effects were reduced by reducing the dosage (Harris et al., J. Urol., 2002, 168(2):542-5). In a second clinical trial, employing a combination of GM-CSF and ketoconazole in men with advanced prostate cancer, slower progression and some growth arrest of prostate cancer was reported (Ryan et al., J. Urol. 2007, 178(6):2372-6).
Treatment of patients with metastatic androgen-independent prostate cancer with a combination of thalidomide and GM-CSF has been shown to lead significant reductions in PSA levels (Dreicer et al., Urol. Oncol., 2005, 23(2):82-86). Dr C. Myers, of the American Institute of Prostatic Diseases, has performed a large-scale clinical trial of a combination of ketoconazole, GM-CSF, transdermal estradiol and hydrocortisone with outstanding therapeutic results (Prostate Forum, C. E. Myers ed., Rivanna Health Publications Inc., 11(9):3-11 (2010), 12(1):3-6 (2011) and 12(2):1-3 (2011)). For any combined drug and immune treatment composition, it is important that the composition includes agents that target replacement of any lost, or impaired, function in other body tissues. For example, ketoconazole affects the adrenal gland and the production of hydrocortisone. The use of estrogens may be indicated to promote bone repair as bone metastatic cancer cells are killed.
The immune system is our natural defense shield providing protection from developing cancers as well as invading microorganisms. However, the immune system is also a barrier to tissue and cell transplantation as it recognizes the transplanted tissue and/or cells as foreign and, in the absence of immunosuppressant therapy, sets out to destroy such transplanted tissues and cells. The human immune system is composed of different blood cell types and their soluble products that together create a system that can sense and kill both infectious disease agents and cancer cells. As shown in FIG. 1, these cells can be divided into innate and adaptive killer cells.
While dendritic cells are innate immune cells, they are generally not killer cells and there are specialized innate killer cells capable of killing cancer cells. Innate immune cells give rise to nonspecific immunity. The innate immune response includes the following characteristics:                There is no learning, memory or lasting protective immunity;        There are a limited number of recognition molecules, or antigens, on the surface of cancer cells that the innate blood cells home to;        Once innate cells are activated, cancer cells can be destroyed within hours; and        The key innate cell types are natural killer (NK) cells, natural killer T (NKT) cells and macrophages.        
All cells have protein “fingerprints” on their surfaces. For white blood cells, these fingerprints are called cluster designation, or CD markers. The CD markers are assigned numbers for identification purposes, and cells are either positive or negative for these markers. These markers allow cells to be distinguished and identified. CD56 is the primary fingerprint for NK cells and NKT cells, which distinguishes them from other cells. In addition to CD56, NKT cells also carry a CD3 marker.
NK cells and NKT cells both kill cancer cells through the release of small cytoplasmic granules of proteins called perforin and granzyme that cause the target cell to die by apoptosis (programmed cell death). NK cells are named “natural killers” because they do not require activation in order to kill cells that are missing “self” markers of major histocompatibility complex (MHC) class I molecules. NKG2D is a type II transmembrane-anchored glycoprotein expressed as a disulfide-linked homodimer on the surface of all human NK cells (NK cells). Stimulation of NK cells through NKG2D triggers cell-mediated cytotoxicity. NKG2D binds to a family of ligands with structural homology to MHC class I molecules. However, unlike conventional MHC class I molecules, NKG2D ligands are frequently over expressed by tumors.
NKT cells are a subset of T cells that co-express a αβ T cell receptor (TCR), but also express a variety of molecular markers that are typically associated with NK cells, such as NK1.1. They differ from conventional αβ T cells in that their TCRs are far more limited in diversity. In addition, unlike conventional T cells that recognize peptide antigen presented by MHC molecules, NKT cells recognize lipid and glycolipid antigens presented by a cell membrane molecule called CD1d. NKT cells include NK1.1+ and NK1.1−, as well as CD4+, CD4−, CD8+ and CD8− cells (Jerud et al., Transfus. Med. Hemother. 2006, 33(1):18-36; Godfrey et al., Nat. Rev. Immunol. 2004, 4(3):231; Vivier et al., Nat Rev Immunol (2004) 4(3):190-198). Invariant natural killer T (iNKT) cells are a subset of NKT cells that express high levels of, and are dependent on, the transcriptional regulator promyelocytic leukemia zinc finger (PLZF) for their development (Savage et al., Immunity, 2008, 29(3):391-403; Kovalovsky et al., Nature Immunology, 2008, 9(9):1055-64). Unlike NK cells, NKT cells are themselves killed in vivo through the interaction of CD95 (Fas) in the NKT cell membrane with CD178 (FasL) and the activation of apoptosis.
In contrast to innate immunity, adaptive immunity is learned immunity and depends mostly on B-cells and T-cells. The characteristics of the adaptive immune response include the following:                T helper cell (Th cells; also known as CD4+ T cells) assist maturation of B cells into plasma cells and activation of cytotoxic T cells and macrophages. Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules that are expressed on the surface of antigen presenting cells (APCs), such as dendritic cells. Once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response. These cells can differentiate into one of several subtypes, including TH1, TH2, TH3, TH17 or TFH, which secrete different cytokines to facilitate a different type of immune response.        Cytotoxic T cells (TC cells or CTLs; also known as CD8+ T cells) destroy virally infected cells and tumor cells. The role of the CD8+ T cells is to monitor all the cells of the body, ready to destroy any that express foreign antigen fragments in their class I molecules. Cytotoxic T cells recognize their targets by binding to antigens associated with MHC class I, which is present on the surface of nearly every cell of the body.        Memory T cells are a subset of antigen-specific T cells that persist long-term after an infection has resolved. They quickly expand to large numbers of effector T cells upon re-exposure to their cognate antigen, thus providing the immune system with “memory” against past infections. Memory T cells comprise two subtypes: central memory T cells (TCM cells) and effector memory T cells (TEM cells). Memory cells may be either CD4+ or CD8+. Memory T cells typically express the cell surface protein CD45RO.        Regulatory T cells (Treg cells), formerly known as suppressor T cells, are crucial for the maintenance of immunological tolerance. Their major role is to shut down T cell-mediated immunity toward the end of an immune reaction and to suppress auto-reactive T cells that escaped the process of negative selection in the thymus. Two major classes of CD4+ regulatory T cells have been described, including the naturally occurring Treg cells and the adaptive Treg cells.        Naturally occurring Treg cells (also known as CD4+CD25+FoxP3+ Treg cells) arise in the thymus and have been linked to interactions between developing T cells with both myeloid (CD11c+) and plasmacytoid (CD123+) dendritic cells that have been activated with TSLP. Naturally occurring Treg cells can be distinguished from other T cells by the presence of an intracellular molecule called FoxP3.A common feature of both prostate and breast cancer is that the phenotype of the disease varies from one patient to another. More specifically, prostate and breast cancers display very heterogeneous cellular morphologies, growth rates, responsiveness to androgen or estrogen hormones and their pharmacological blocking agents, and metastatic potential, in different individuals. This heterogeneity in cancer phenotype is reflected in the effectiveness of different treatment compositions used by physicians, in that different prostate or breast cancer phenotypes are responsive to very different drug compositions. This is a major problem for physicians when determining the best treatment protocol for individual patients. Furthermore, the advancements in diagnostic methods for both prostate and breast cancer have failed to solve the problems facing the cancer specialist. For example, current diagnostic techniques are unable to determine whether each newly diagnosed prostate or breast cancer is an indolent, non-life threatening, form of the disease, or a virulent form capable of lethality; whether the cancer is contained in the prostate or breast, or whether it will, or has metastasized; and which drug composition is likely to be most effective in treating the disease.        
There thus remains a need in the art for methods that assist physicians to better select drug treatments, and in particular combination drug compositions for individual patients with prostate cancer or breast cancer, and for methods for monitoring the efficacy of treatment protocols.